Field of the Invention
The present invention relates to a lens barrel and an optical apparatus having the same.
Description of the Related Art
A lens barrel used for an optical apparatus such as a digital camera or a video camera and the like has a mechanism that moves lens holding members (lens holding frames) holding lens groups in a direction of an optical axis (optical axis of a imaging optical system) during, for instance, focusing by means of rotation of a rotary cylinder (cam cylinder).
In this mechanism, the cam cylinder having cam grooves, a guide cylinder (stationary cylinder) having a longitudinal groove (rectilinear groove) parallel to the direction of the optical axis, and cam followers engaged with both of grooves are used. The cam followers are fixed to the lens holding frames by screws, or the like. As the cam followers move in the direction of the optical axis due to rotation of the cam cylinder, the lens holding frames move in the direction of the optical axis.
In this lens barrel, the cam cylinder is rotated for zooming, and the plurality of lens holding frames supported in the plurality of respective cam grooves formed in the cam cylinder move. Especially, in a zoom lens of high power, the plurality of lens holding frames have different amounts of movement and great amounts of driving. For this reason, it was difficult to dispose the plurality of cam grooves having different trajectories on a circumference of the single cam cylinder in light of a space.
In a zoom lens device (lens barrel) disclosed in Japanese Patent Laid-Open No. 2007-264220, when a magnification is varied by driving a cam cylinder itself, each lens holding frame has an amount of movement that is divided into displacement of a corresponding cam groove provided in the cam cylinder in a direction of an optical axis and displacement of the cam cylinder itself in the direction of the optical axis. This reduces a length of each cam groove provided in the cam cylinder, and a plurality of cams for driving the respective lens holding frames are disposed in a space on a circumference of the cam cylinder.
Even in the lens barrel disclosed in Japanese Patent Laid-Open No. 2007-264220, it is still necessary to provide the cam grooves on the circumference of the cam cylinder equal in number to the movable frames such as the lens holding frames. Accordingly, when an attempt is made to dispose all of the plurality of cam grooves, the cam cylinder requires a length in the direction of the optical axis, and it is necessary to increase a diameter of the cam cylinder.